If you want something more than a Twist 1300 but smaller than an MVP, you are definitely in mod land. Maybe a Reo mini, or something along the lines of a Provari Mini or MVari Mini.
As for a better tank, then definitely check out the Kanger line. The EVOD, The T3s, MT3s, Unitank Mini, or Protank Mini. There is also the Smoktech Aro, the Vsision Victory BCC, or the Vapeonly BCC.